Because a non-volatile memory retains stored data even when there is no power supply, it is often used for data storage in systems such as a personal computer (PC) basic input/output system (BIOS), a set-top box, a printer, and a network server. Recently, non-volatile memory is being used in digital cameras and mobile phones.
One common non-volatile memory is an electrically erasable programmable read-only memory (EEPROM) flash memory device. In the EEPROM flash memory device, during a programming operation, channel hot electrons form in a drain region to accumulate electrons in a floating gate, such that a threshold voltage of a cell transistor is increased.
Then, during an erasing operation, the EEPROM flash memory device generates a high voltage to discharge the electrons accumulated in the floating gate, such that a threshold voltage of a cell transistor is decreased. An EEPROM flash memory device can electrically erase data of a memory cell simultaneously or according to sector unit.
As the degree of integration continues to increase, the miniaturization of a cell size becomes extremely important. However, because the floating gate cell requires a high voltage during programming or erasing operations, and because it is difficult to obtain a process margin for tunnel definition, further miniaturization is becoming extremely difficult and may be almost impossible.
Due to the above limitations, research for non-volatile memory devices substituting a floating gate cell is under active development.